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BackgroundSelf-reported body weight is often used for calculation of Body Mass Index because it is easy to collect. Little is known about sources of error introduced by using bathroom scales to measure weight at home. The objective of this study was to evaluate the accuracy and consistency of digital versus dial-type bathroom scales commonly used for self-reported weight.MethodsParticipants brought functioning bathroom scales (n = 18 dial-type, n = 43 digital-type) to a central location. Trained researchers assessed accuracy and consistency using certified calibration weights at 10 kg, 25 kg, 50 kg, 75 kg, 100 kg, and 110 kg. Data also were collected on frequency of calibration, age and floor surface beneath the scale.ResultsAll participants reported using their scale on hard surface flooring. Before calibration, all digital scales displayed 0, but dial scales displayed a mean absolute initial weight of 0.95 (1.9 SD) kg. Digital scales accurately weighed test loads whereas dial-type scale weights differed significantly (p < 0.05). Imprecision of dial scales was significantly greater than that of digital scales at all weights (p < 0.05). Accuracy and precision did not vary by scale age.ConclusionsDigital home bathroom scales provide sufficiently accurate and consistent weights for public health research. Reminders to zero scales before each use may further improve accuracy of self-reported weight.

Background. Parent-reported measurement of child height is common in public health research but may be inaccurate, especially for preschoolers. A standardized protocol and tools to improve measurement accuracy are needed. The purpose of this study was to develop and test materials to improve parents' accuracy when measuring their preschooler's height. Methods. In Phase A, 24 parents were observed measuring child height using written instructions and an easy-to-read tape measure; after each of 3 testing rounds, instructions were refined based on observed errors and parent versus researcher measurements. In Phase B, a video replaced written instructions and was refined over 4 rounds with 37 parents. Results. The height kit with written instructions, tape measure, plumb line, and explanatory video helped parents accurately measure child height. Compared to written instructions alone, parents rated the video as having significantly greater clarity and likelihood of improving measurements. Although no significant differences in accuracy were found between paper and video instructions, observations indicated written instructions were more difficult for parents with less education to use with fidelity. Conclusions. The kit may improve parent measurement of preschooler height, thereby improving accuracy of body mass index calculations, tracking of obesity prevalence, and obesity prevention and treatment.

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